System for injecting water, collected from a subterranean aquifer, into an oil reservoir

ABSTRACT

The invention relates to a system for collecting and injecting water from a subterranean aquifer directly into hydrocarbon reservoirs. The system may include a collecting wells in aquifers, injection wells in hydrocarbon producing reservoirs and a hydraulic connection for pumping water with access to a collecting zone and to an injection zone. The invention is applicable to hydrocarbons production fields, where water injection is used to maintain the pressure in a hydrocarbon producing reservoir, thereby enhancing the recovery rate of the same.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to Brazilian Application No. PI0404603-0, filed Oct. 22, 2004, entitled “SISTEMA DE INJE

ÃO DE ÁGUA CAPTADA EM AQUIFERO SUBTERRÂNEO E PO

OS INJETORES EM RESERVATÓRIO DE ÓLEO,” and incorporates the same herein by reference in its entirety. This application also is a Continuation-In-Part of prior U.S. application Ser. No. 11/256,361, which was filed on Oct. 21, 2005, and incorporates the same herein by reference in its entirety.

TECHNICAL FIELD

The present invention relates to a system for collecting and injecting water from a subterranean aquifer into hydrocarbon reservoirs and, more specifically, a system of water collecting wells in subterranean aquifers and of injection wells in hydrocarbon producing reservoirs, wherein one or more pumps may be utilized to improve injection rate. The invention is applicable in hydrocarbon production systems, where water injection is utilized to maintain hydrocarbon producing reservoir pressure, thereby enhancing recovery of the same.

BACKGROUND OF THE INVENTION

One of the principal methods of secondary recovery, known and employed in the field of hydrocarbon reservoir, especially in subsea petroleum, utilizes water injection to maintain the pressure in hydrocarbon producing reservoirs.

Typically this water is collected and treated directly from the sea and/or from water produced jointly with the hydrocarbons.

U.S. Pat. No. 6,149,458 teaches the installation of a Submersible Centrifugal Pump (SCP) within a dummy well for injecting water into injection wells. However, the system has the following deficiencies: it requires the construction of a shallow well for installation of the pump and a water treatment unit is required to treat the water to be injected, which has been collected from the sea and/or produced jointly with the hydrocarbons.

In Petrobras' Brazilian Patent application PI 0400926-6 a method of installing a pump in a dummy well, in this case an oil production well, is also disclosed.

The principal deficiencies in the current state of the art include the high cost of treating the collected water, as well as the reliability of the quality of the water being treated and injected into the well. In addition, the method utilized for collecting and injecting water results in the injected water having a temperature which approximates that of the low temperature water found at the ocean floor.

For hydrocarbons, in general, and especially for heavy oils, it is highly desirable and advantageous that the water be injected at a temperature which is higher than that found at the ocean floor. Water, injected under these conditions, facilitates the dislodgement and scouring of the reservoir. Another difficulty in the current state of the art is the installation of a water injection pump.

Some existing models of compact pumps may be installed on the ocean floor in skids or may be integrated into a wellhead. However, utilizing submersible centrifugal pumps has certain advantages. Notably, submersible centrifugal pumps are produced on a large scale and at a low cost. Furthermore, submersible centrifugal pumps possess a slender geometry which requires the drilling and construction of dummy wells for accommodating the same, as described in the patents above.

The disadvantages in the state of art discussed above are remedied by using an injection system which utilizes water collected from subterranean aquifers.

More specifically, present invention presents a system of water collecting wells in aquifers and injection wells in hydrocarbon producing reservoirs which provides a means of maintaining pressure in the reservoirs by injecting water, of higher quality and at a higher temperature, thereby dispensing with a water treatment unit and reducing the costs of installation and operation of stationary units in subsea petroleum production fields.

In this way, it is possible to maintain hydrocarbon producing reservoir pressure by injecting water having a good quality and higher temperature than that presently achieved in the state of the art, thereby increasing productivity and the oil recovery factor of the reservoir.

Another application of this invention is in mature fields where there is no space on existing platforms for the construction or enlargement of the existing water injection unit.

SUMMARY OF THE INVENTION

Systems consistent with the invention enable water collection from subterranean aquifers and direct injection of that water into hydrocarbon producing reservoirs to maintain pressure in the reservoirs.

The collection of water in subterranean aquifers is accomplished by means for collecting water, as a collecting well. This collected water may be pressurized by means of a submarine pump and thereafter injected through injection wells, whose points of destination are located at the base of the hydrocarbon producing reservoirs or in an active aquifer in the oil reservoir.

The hydraulic connection that pumps water from a collecting zone in a well to a injection zone of a hydrocarbon reservoir may be accomplished in accordance with the following embodiments as illustrate the drawings:

(1) a hydraulic connection on the seabed with underwater pipelines linking at least one collecting well with at least one injection well, a pump being installed on the seabed or on the collection well itself;

(2) a hydraulic connection inside a single or multilateral well, with access to the collection zone and to the injection zone; and

(3) a hydraulic connection outside of a single or multilateral well, with access to the collection zone and to the injection zone.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a basic embodiment of the invention wherein a conventional collecting well is linked through submersible pipelines to one or more injection wells, and an injection pump is installed externally between the collecting well and the injection well on a metallic structural base, a dummy well or other adequate means.

FIG. 2 illustrates another embodiment of the invention wherein at least two wells (a collecting well and an injector well) are externally linked. The injection pump is installed within the collecting well, thereby avoiding the need for installing a Wet Christmas Tree (WCT).

FIG. 3 illustrates another embodiment of the invention wherein the pump is installed within a multilateral well linking the collecting zone to the water injection zone.

FIG. 4 illustrates another embodiment of the invention wherein a pump is installed outside a multilateral well linking the collecting zone to the water injection zone in the same well.

FIG. 5 illustrates another embodiment of the invention wherein a pump is installed outside a conventional well, linking the collecting zone to the water injection zone in the same well.

FIG. 6 illustrates another embodiment of the invention wherein a pump is installed within the interior of a conventional well, linking the collecting zone to the water zone in the same well.

FIG. 7 illustrates another embodiment of the invention wherein a pump installed inside or outside a multilateral well can inject collected water at different locations within the injection zone.

In summary:

Fig No. of Wells Type of well Pump location 1 >=2 Conventional Outside 2 >=2 Conventional Inside 3 1 Multilateral Inside 4 1 Multilateral Outside 5 1 Conventional Outside 6 1 Conventional Inside 7 1 Multilateral Outside

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

A system for collecting water from subterranean aquifers and injecting that water directly into hydrocarbon producing reservoirs is described in accordance with the following embodiments:

(1) a hydraulic connection on the seabed with underwater pipelines linking at least one collecting well with at least one injection well, a pump being installed on the seabed or on the collection well itself;

(2) a hydraulic connection inside a single or multilateral well, with access to the collection zone and to the injection zone; and

(3) a hydraulic connection outside of a single or multilateral well, with access to the collection zone and to the injection zone.

In the first embodiment (1), the hydraulic interface occurs at the ocean floor through underwater pipelines which link at least one collecting well with at least one injection well. Since this construction requires at least two independent wells, the collecting well and the injector well, production costs are increased compared to an embodiment with one well. In addition, the temperature of the water being injected is reduced, due to the substantial thermal exchange which occurs between the collected water and the sea water over the length of the submarine line which connects the wellheads of the wells (i.e., of the collection well and the injection well).

The injection pump may be located outside of the wells, thereby permitting it to be removed and reinstalled by means of a cable from a low daily cost vessel. This solution presents greater flexibility in the spacing between the point of collection and the point of injection. In this embodiment the design of the wellhead, collection column and injection column are conventional.

Alternatively, the pumping unit may be installed in the collecting well, without the need for a Wet Christmas tree (WCT).

In the second embodiment (2) above, both the pumping unit and the hydraulic connection between the collecting well and the injection well are located inside a conventional or multilateral well which has access to the collecting and injection zones. This embodiment eliminates the need of two wells (for collecting and injecting) and maintains the injection water at a higher temperature by avoiding thermal exchange with sea water on the ocean floor, which is generally colder. In this case, with the injection pump being positioned inside the well, maintenance will require the use of a rig, with higher costs.

In the third embodiment (3) above, the pumping unit and the hydraulic connection between the collecting well and the injector well are located outside a conventional or multilateral well, thereby facilitating the removal and reinstallation of the injection pump and hydraulic connection via cable from a low daily cost vessel. There is a substantial reduction in costs due to the need of only one well with dual functions, i.e., collecting and injecting water, as opposed to the need of two wells embodiment. Furthermore, the temperature of the water being injected is higher because there will be no substantial thermal exchange between the collected water on the ocean floor, which is generally much colder.

Therefore, a system for direct injecting water, collected from a subterranean aquifer, into a hydrocarbon producing reservoir, comprises:

-   -   means for collecting water from a subterranean aquifer;     -   at least one well;     -   an injection pump that pumps the collected water into the         hydrocarbon producing reservoir through a injection well; and     -   a direct hydraulic connection between a collecting zone of the         subterranean aquifer and an injection zone of the oil reservoir,         the hydraulic connection comprising at least one submersible         pipe.

In accordance with the following description, based on the drawings, the reference numbers are:

1. Collecting well

2. Injection well

3. Injection Pump

4. Directional or Horizontal (Conventional) well

5. Annular space

6. Multilateral well

7. Collection column

8. Injection column

9. Telescopic assembly (Tubing Seal Receptacle (TSR))

10. Obturator (Tubing Packer Hanger)

11. Injection control element

12. Wellhead

13. Injection zone

14. Collecting zone

15. Water collection line

FIG. 1 is a general schematic view of an embodiment of the invention with a hydraulic connection positioned externally between the collecting well 1 and one or more injector wells 2. An injection pump 3 is installed outside the two wells, either on a metallic structural base or in a dummy well, coupled to the wellhead or secured by any other means. In this way, the water collected through the collecting well 1 is pressurized by the injection pump 3 and is injected into one or more injection wells 2.

FIG. 2 is a general schematic view of another embodiment of the invention wherein an injection pump 3 is installed inside in the collecting well 1 and the hydraulic connection between the collecting well 1 and the injection well 2 (not shown in the drawing) is the wells 1, 2.

In this embodiment, there is no need to install a WCT in the collecting well 1, and a collection column 7 is seated and positioned approximately hundred meters below the wellhead 12 by an obturator (tubing packer hanger) 10.

An injection pump 3, encapsulated in a small section of mounting tubing, is installed between the tubing packer hanger 10 and the wellhead 12. An injection control element 11, such as a valve, is installed in a portion of the collecting column 7, located below the tubing packer hanger 10, which can be operated remotely to block the collecting well 1 in the event of an intervention on the same. Said injection control element 11 may be hydraulic or electric.

In the event of a failure in the injection pump 3, the pump may be retrieved without the necessity of removing the collection column 7, since a telescopic assembly 9, installed between the tubing packer hanger 10 and the injection pump 3, facilitates the assembly and disassembly.

Since safety concerns are less critical in the operation of a collecting well 1, the control of such a well may be accomplished by an injection control element 11. This eliminates the need for installing a WCT for this purpose, thereby reducing installation and maintenance costs. In this way, it is possible to connect the water collection pipeline 15 directly to the wellhead 12.

FIG. 3 is a general schematic view of an embodiment of the invention wherein both the injection pump 3 and the hydraulic connection between the collection zone 14 and the injection zone 13, are positioned within the interior of a multilateral well 6. The collecting column 7 is hydraulically linked to a suction orifice of the injection pump 3 and the discharge flow is injected into the injection zone 13 through the injection column 8.

FIG. 4 is a schematic view of another embodiment of the invention wherein the hydraulic connection between the collecting zone 14 and the injection zone 13 is located inside a multilateral well 6 by means of an injection pump 3 positioned outside of the multilateral well 6.

The water in the injection zone flows through the annular space 5 to the suction orifice of the injection pump 3 where it is pressurized and returns through the injection column 8 to the injection zone 13.

FIG. 5 illustrates an embodiment of the invention wherein an injection pump 3 is installed outside a conventional well 4, which links the collecting zone 14 to the water injection zone 13. The collected water flows through the annular space 5 to the injection pump suction orifice, where it is pressurized, thereafter returning through the injection column 8 to the injection zone 13.

FIG. 6 illustrates an embodiment of the invention wherein an injection pump 3 is installed in the injection column 8, which itself is positioned inside a conventional well 4. The water collected in the collecting zone 14 is pressurized by the injection pump 3 and flows through the injection column 8 until reaching the injection zone 13.

FIG. 7 illustrates an embodiment of the invention wherein a multilateral well 6 has an injection pump 3. Said injection pump 3 may be installed inside or outside (not shown in the drawing) the multilateral well. In this embodiment of the invention, it is possible, with a single multilateral well 6, to inject water into more than one injection zone 13. In this embodiment, each injection zone 13 includes an injection control element 11, e.g., a type of valve. Water may be collected from one collecting zone 14 inside a multilateral well 6 or from another collecting well, not shown in FIG. 7, specific to this purpose.

Although the present invention has been described according to its preferred embodiments, it should be obvious to one skilled in the art that various embodiments are possible without departing from the scope of this invention, which is defined by the claims appended hereto. 

1. A system for injecting water, collected from a subterranean aquifer, into a hydrocarbon reservoir, the system comprising: means for collecting water from a subterranean aquifer; an injection pump that pumps the collected water into the hydrocarbon producing reservoir through at least one injection well; and a direct hydraulic connection between a collecting zone of the subterranean aquifer and an injection zone of the hydrocarbon producing reservoir, the hydraulic connection comprising at least one submersible pipe.
 2. The system, according to claim 1, wherein the means for collecting water is a collecting well.
 3. The system, according to claim 2, wherein the well is a conventional well.
 4. The system according to claim 2, wherein the well is a multilateral well.
 5. The system according to claim 3, wherein the collecting zone and the injection zone are located in the same well with access to the collecting zone and to the injection zone.
 6. The system according to claim 4, wherein the collecting zone and the injection zone are located in the same well with access to the collecting zone and to the injection zone.
 7. The system according to claim 3, wherein the injection pump is installed outside the well.
 8. The system according to claim 4, wherein the injection pump is installed outside the well.
 9. The system according to claim 3, wherein the injection pump is installed inside the well.
 10. The system according to claim 4, wherein the injection pump is installed inside the well.
 11. The system according to claim 1, wherein the at least one injection well comprises a plurality of injection wells. 